1. Field of the Invention
The present invention relates generally to methods for determining the rotor blade angle of a wind power installation, including the ability to measure the blade angle from ground level.
2. Description of the Related Art
In pitch-regulated wind power installations the angles of the rotor blades can be adjusted synchronously (standard construction) or independently of each other. The construction for adjustment independently of each other is described in patent application DE 197 31 918. That design can also be referred to as on-line individual blade adjustment. Whether the blades are adjusted synchronously or independently, it is important that an initial blade angle, for example feathered position or maximum blade angle, can be set with a sufficient degree of accuracy.
Moreover, when the synchronous mode of operation is involved, it is necessary to ensure that all blades are adjusted to the same angle. In other words, the relative angle of the rotor blades with respect to one another should be equal to zero.
Maladjustments of the rotor blade angles, which can arise, for example, from manufacturing tolerances (or manufacturing errors) such as displaced zero degree markings or displaced blade connecting bolts, can result in defective operation (wrong rotary speed-output power characteristic) or unbalance phenomena (and thus pylon oscillations and vibrations). Such maladjustments can also result in increased loadings on the components of the installation.
In the known prior art, if after the wind power installation is brought into operation and a defective blade angle setting is suspected, operation is usually implemented with blade jig templates. Jig templates are pushed over the blade tips as far as a defined position on the rotor blade and, with the blade in a horizontal position, a sensor on the jig template measures the angle of the plane of the blade to the surface of the earth (plumb angle). By further 180° rotation of the rotor and renewed measurement, possible inclined positionings of the pylon or any rotor axis angles that may be present are averaged out and the procedure gives the absolute angle of the respective rotor blade.
Even with the advent of sensor systems, which permit wireless data transmission, the above method is costly and complicated, especially with regard to large rotor blades where large jig templates are needed. Applicant therefore believes it is desirable and possible to provide an improved method for determining the rotor blade angle of a wind power installation. The present invention provides such a method.